What Will Happen After The 'Big One' Hits SoCal?

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Over a decade has passed since Hurricane Katrina brought destruction to New Orleans and the Gulf Coast, leaving 1,245 dead and $108 billion in property damage. More than a million people were displaced and communities destroyed. The region has come a long way since then, but it will never be the same. Katrina remains the country’s worst natural disaster.

Here in Southern California, earthquakes, rather than hurricanes, pose risks to our lives, health, and socioeconomic futures. The risks are more pronounced in dense areas -- places where there are more people and infrastructure that can be affected. This is true of all natural disasters. The ten counties that make up Southern California (from San Luis Obispo and Kern in the north to San Diego and Imperial counties to the south) are home to 22.7 million people and an economy greater than $1 trillion. A major earthquake, sometimes referred to as the "Big One,” could easily be twice as damaging as Katrina.

It may not be possible to precisely predict the next seismic event, but scientists have studied likely scenarios and modeled their impacts on Southern California. In 2008, the U.S. Geological Survey published a 312-page report detailing what would happen if a magnitude 7.8 earthquake struck, rupturing along the San Andreas fault. The report modeled physical damages, emergency response, economic consequences, and long-term recovery for the region. If you’ve heard any statistics about the "Big One," it probably came from this report.

The portion of the San Andreas Fault that scientists modeled stretches from the Salton Sea, northwest through Riverside, San Bernardino and Los Angeles counties, up to Lake Hughes, northwest of Palmdale. The ShakeOut scenario, as scientists call it, starts with a rupture in the southwest corner of the Salton Sea. It would take about 90 seconds to reach Lake Hughes, but the overall shaking wouldn’t stop for nearly four minutes. This portion of the San Andreas Fault crosses roads in 996 places, the I-10, I-15, CA-15, CA-111, and CA-62. Also, there are 90 fiber optic cables, 39 gas pipelines, 21 railroads, 32 aqueducts, and 141 overhead electrical power transmission lines that cross the fault.

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The earthquake would cause $35 billion in damages to buildings, and more than $10 billion in damaged or lost goods. More than half of the damage would be to residential buildings -- single-family homes (29%), and apartments and other residences (25%). Commercial buildings would suffer 31% of the losses, while industrial and other buildings would suffer the remaining 15% of damage. The buildings closest to the rupture would suffer the most damage, especially mobile homes. The hardest hit regions would be San Bernardino, San Gabriel Valley, Coachella Valley, and Palmdale.

quake graph


Fires sparked by the earthquake, such as from broken gas lines, would bring greater damage than the shaking itself. About 1,600 fires would start, 1,200 of which would be too large for one fire company to put out on its own. Damage to the water system would hinder firefighting efforts. Traffic gridlock would slow down fire fighters. Damage to buildings and their contents would reach $65 billion.

Total direct damage (buildings, fires, and other) from the earthquake would be $112 billion. But beyond the immediate damage caused by the earthquake, economic impacts from damages to infrastructure and disruption to businesses, industry and trade would continue to be felt. One major industry in Southern California is trade and logistics. 40% of imports for the United States pass through the ports of Long Beach and Los Angeles. Because of this, the Inland Empire is a hub for transportation and logistics. The vast majority of cargo is transported by trucks within the region (see graphic below). Damaged infrastructure would hinder the movement of goods as well as people throughout. This means increased operating costs and loss of time during commutes.

quake bar graph
Southern California freight in millions of tons.


Utilities would be a significant factor in economic recovery. Communications would likely be restored first, followed by electricity, gas, and finally water. Most people would get utilities restored relatively quickly, but some for some it could take longer than two weeks. Water would be the slowest utility to restore. It could take as long as six months to reach the final group of customers -- this means a loss in productivity. Slow water service recovery is the most costly setback, bringing about more than half of the indirect losses ($53 billion). Total indirect economic losses brought on by damaged or lost infrastructure would reach $96 billion. This calculation includes the multiplier effect -- how spending spurs further economic activity.

The entire economic impact of the ShakeOut scenario is a $213 billion economic loss. At nearly twice what Katrina cost, it would become the most costly natural disaster in United States history. But experts say that, compared to Katrina, it wouldn’t be as devastating. The damage is higher overall, but the size and diversity of Southern California’s economy means that the losses would be easier to absorb.


Top Image: Collapsed double-decker freeway structure in Oakland, California | Public Domain

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